Perfluoropolyether (PFPE) compounds are excellent in heat resistance, chemical resistance, and oxidation resistance. In addition, since perfluoropolyether compounds have a large viscosity index, changes in fluidity (viscosity) are also small in a wide temperature range from low temperatures to high temperatures. Therefore, perfluoropolyether compounds exhibit favorable lubricity. Moreover, perfluoropolyether compounds are incombustible and have almost no adverse effects on the polymer-based materials such as rubbers, plastics, and the like. Furthermore, perfluoropolyether compounds also have properties such as low vapor pressure and low evaporation loss, low surface tension, and high electrical insulating properties. Therefore, perfluoropolyether compounds are known to exhibit high performance over an extremely wide range as lubricants. For this reason, they are widely used in the vacuum pump oil and the lubrication of a magnetic disk/tape or the like as a lubricating oil, a heating medium, a non-pressure-sensitive adhesive and other applications. Since perfluoropolyether compounds are excellent in heat resistance, chemical resistance and oxidation resistance, they can also be used in special applications such as the packing rubbers in chemical plants as fluorine resins, such as perfluoroelastomers, fluororubbers, PTFE, and PFA. Because such fluororesins are used in very harsh conditions, further improvements of heat resistance in particular have been required.
On the other hand, C60 which is a type of fullerene has been known to be useful as a lubricant. In Non-Patent Document 1 (Bhushan et al.: Appl. Phys. Lett. 62, 3253 (1993)), the reduction of the friction coefficient has been confirmed in a silicon substrate where a vapor-deposited film of C60 has been formed. In Non-Patent Document 1, a fullerene derivative obtained by introducing a perfluoropolyether group into a fullerene has also been proposed. However, there is no description with regard to specific compounds or their production method.
Moreover, C60 is known to exhibit excellent properties as an additive to conventional lubricating oils. In Non-Patent Document 2 (Ginzburg et al.: Russian Journal of Applied Chemistry 75, 1330 (2002)), the frictional resistances of those obtained by applying an ordinary lubricating oil onto the surface of a copper foil and those obtained by applying the oil added with 5% of C60 have been measured. The frictional resistance was measured by rubbing a steel roller while applying a load. As a result, it has been confirmed that the abrasion resistance improves when C60 is added, as compared with the case where no addition was made.
In Patent Document 1 (Japanese Unexamined Patent Application, First Publication No. 2006-131874), a lubricant composed of a mixture of C60, a C60 derivative having a carboxyl group, a hydroxylated fullerene or a fullerene derivative having an ester group, and a perfluoropolyether has been described.
In addition to this, fullerene derivatives have been used in various fields. In Patent Document 2 (Japanese Unexamined Patent Application, First Publication No. 2013-140923) and Patent Document 3 (Japanese Unexamined Patent Application, First Publication No. 2013-170137), a fullerene derivative having one perfluoropolyether group in the molecule as an n-type semiconductor material has been described.
In Patent Document 4 (Japanese Unexamined Patent Application, First Publication No. Hei 10-310709), a crystalline thermoplastic resin composition obtained by adding 0.1 to 2,000 ppm of carbon cluster (fullerene) with respect to a crystalline thermoplastic resin has been disclosed. The crystalline thermoplastic resin composition has a high crystallization rate, so that excellent properties of the crystalline thermoplastic resin are not impaired. In addition, mechanical properties and in particular, the molding cycle is favorable.
In Patent Document 5 (Japanese Unexamined Patent Application, First Publication No. Hei 8-49116), fibers, films or hollow bodies that contain a polyester and fullerene and have an individual fiber titer of less than 10 dtex have been disclosed.
In Patent Document 6 (Japanese Unexamined Patent Application, First Publication No. 2006-117760), a polyester-based resin composition in which fullerenes are dispersed on the order of nanometers has been disclosed. The dispersion of fullerenes has been realized by producing the polyester resin composition using a fullerene solution.